Double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board and wiring circuit board

Abstract

The present invention provides a double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board, which includes a pressure-sensitive adhesive layer formed by a pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition contains an acrylic polymer as a main component and further contains an electrically conductive filler in a proportion of 5 to 100 parts by weight with respect to 100 parts by weight of a total solid in the pressure-sensitive adhesive composition except the electrically conductive filler. The double-sided pressure-sensitive adhesive tape or sheet is excellent in adhesiveness, electrically conducting property and anti-repulsion property, and thus can be advantageously used for wiring circuit board.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board and a wiring circuit board.BACKGROUND OF THE INVENTION[0002]In electronic instruments, wiring circuit boards are used and, with regard to the wiring circuit board, a flexible printed circuit board (may be sometimes called “FPC”) has been widely used. Usually, wiring circuit boards such as FPC are used in a state of being adhered to a reinforcing plate (such as aluminum plate, stainless steel plate or polyimide plate) and, at that time, a double-sided pressure-sensitive adhesive tape or sheet (double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board) is used. With regard to such a double-sided pressure-sensitive adhesive tape or sheet, a double-sided pressure-sensitive adhesive tape or sheet having a constitution of being formed only by adhesive layers (so-called “double-sided pressure-sensitive adhesive tape or sheet wi...

AI Technical Summary

Benefits of technology

[0006]Accordingly, an object of the present invention is to provide a double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board, which has an electrically conducting property. Another object of the present invention is to provide a double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board, which has a high adhesiveness as well as an excellent anti-repulsion property even being subjected to a high-temperature step. Further, another object of the present invention is to provide a double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board, which is able to suppress or prevent the self-adhesion of the cut surfaces after a cutting process and has an excellent fine processing property. Further, another object of the present invention is to provide a wiring circuit board in which the double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board is used.

[0007]In order to achieve the above-mentioned objects, the present inventors have carried out intensive investigations and found that, when a pressure-sensitive adhesive layer is formed by a pressure-sensitive adhesive composition which contains an acrylic polymer as a base polymer and an electrically conductive filler in a specific amount, the double-sided pressure-sensitive adhesive tape or sheet suitably used for a wiring circuit board, which has a good adhesiveness to a wiring circuit board and reinforcing plate and exerts an electrically conducting property, can be obtained. Further, the present inventors have found that, when a solvent-insoluble fraction of the pressure-sensitive adhesive layer in the initial stage and a solvent-insoluble fraction after a solder reflow step under specific heat treatment conditions with respect to the solvent-insoluble fraction in the initial stage are adjusted to a specific range, an excellent anti-repulsion property can be achieved even being subjected to a high-temperature step by a solder reflow step and thus a good adhesiveness can be retained even when used to the part where repulsion takes place. Further, the present inventors have found that, when the tape has the above-mentioned specific pressure-sensitive adhesive layers on both surfaces of a substrate, the self-adhesion of the cut surfaces after a cutting process is suppressed or prevented and thus fine processing property is improved. The present invention has been accomplished based on these findings.

[0031]Since the double-sided pressure-sensitive adhesive tape or sheet for wiring circuit board according to the present invention has the above-mentioned constitution so as to have an electrically conducting property, it is useful for removing static electricity of the wiring circuit board. Further, it has a good adhesiveness and, even after being subjected to a high-temperature step, it can exert an excellent anti-repulsion property. Further, it is possible to suppress or prevent the self-adhesion of the cut surfaces after a cutting process and it is also excellent in fine processing property.

Problems solved by technology

However, since the double-sided pressure-sensitive adhesive tape or sheet without substrate has no substrate, it is not suitable for fine perforating process.

Moreover, there is a problem in the conventional double-sided pressure-sensitive adhesive tape or sheet that, especially under the conditions of high temperature and high humidity, the cut surfaces are adhered again (self-adhesion) after being perforated whereby working ability lowers.

Further, in the worst case, it sometimes happens that, in detaching the perforated product, a part where a pressure-sensitive adhesive layer is deficient is resulted.

Although it has been attempted that, in the pressure-sensitive adhesive layer, matters insoluble in a solvent are increased for preventing the self-adhesion of the cut surfaces (refer to JP-A-2001-40301), there is a problem that, when the matters insoluble in a solvent are increased, the pressure-sensitive adhesive layer is peeled off from the adherend when it is adhered to a part of the adherend on which repulsive force it applied.

On the other hand, in wiring circuit board such as FPC, there are some cases where a high-temperature step such as a solder reflow step is conducted but, when the pressure-sensitive adhesive layer is adhered to a part of an adherend on which a repulsive force is applied after the solder reflow step, a problem that the pressure-sensitive adhesive layer is peeled off from the adherend arises in some cases.

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